jenk

[A]erobic exercise helps the heart pump more blood to the brain, along with the rest of the body. More blood means more oxygen, and thus better-nourished brain cells. For decades, that has been the only link between athletic and mental prowess that science has been able to demonstrate with any degree of certainty.
[...]
Active adults have less inflammation in the brain. They also have fewer "little bitty strokes that can impair cognition without the person even knowing," says University of California, San Francisco, neuroscientist Kristine Yaffe. Still other researchers have found that athletes have more astrocytes, or cells that support neurons and mop up neurotransmitters after they're used to send messages from cell to cell. And even the levels of those neurotransmitters are higher in people who exercise frequently. "Dopamine, serotonin, norepinephrine—all of these are elevated after a bout of exercise," says [Harvard psychiatrist John Ratey]. "So having a workout will help with focus, calming down, impulsivity—it's like taking a little bit of Prozac and a little bit of Ritalin."
[...]
So far, though, for reasons that no one really understands, the few studies that have examined stretching, toning and weight lifting have found little to no effect on cognition.

- Full article at Newsweek